OF THE GENE
, MOLECULAR BIOLOGY OF THE GENE
20th
in
century
researchers
already knew that
genetic material must be
1 . able to store information that pertains to development
, structure and metabolic activities of
cell
/organism
. stable
2 so that it can be replicated with
high accuracy transmitted to next generation
-o
,
(mutations
3
. able to
undergo rare
changes provide
genetic variability required for evolution
-
material established but structure still unknown
by 1950 DNA as
genetic was
contains four different of nucleotides
it was known that DNA
types
↳
two - adenine
purine bases (A) quanine (G) double
with have
ving
=
,
(T)
Cytosine (C)
↳ two
with
pyrimidine bases
thymine have
single ring
- =
,
O
NHz
C C13
adenine
(A) & thymine
(T)
IN
↓N C
CIA nitrogen-containing O D CIA
I base
O
N N N
O
HOPOSCH2 H0P05CH2 g
O
4 Cy O
4 Cy
# 1* # 1*
sugar = deoxyribose
3
②021 C 02 ,
1 NHz
3
g
81 H 81 H
guanine C cytosine * C
a
I N
(G) (C)
G ②C
HzN
W
O O
H0P05CH2 g HOPOSCH20g
O
4 1C O
4 Cy
# # 1*
3
②021 3
②021
81 H 81 H
Erwin
Chargaff analyzed base content of DNA
↳ showed that
of of nucleotide but most do not , DNA
some species have
roughly 25 % each
type -
of various spaces differs
↳ e in humans A and T is about 31 %, so nucleotide content not fixed across species DNA does
g
=
. .
have
variability
within species DNA is consistent
Chargaft's rules :
. amount
1 of A , T , G and (varies from species to species
2 .
in each species ,
amount of A =
T ,
and amount of G =
C
of four bases possible
only at each nucleotide position in DNA sheer number of bases and
length of
to
one
most DNA molecules provide for variability
↳ human chromosome -
140 million base pairs